Basic specs
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Basic specs

Despite its relatively modest zoom range, the 25-50mm F1.7 is a complex lens, featuring 16 elements in 11 groups. This includes one aspherical element, three extra-low dispersion (ED) elements and a single ultra-high refractive index (UHR) element. It has 9 rounded aperture blades to give circular bokeh (in the middle of the frame, at least).

The minimum focus distance ranges from 28cm (11") at the wider end to 31cm (12.2") at the 50mm setting. This provides it with a maximum magnification of 0.21x (0.42x in full-frame terms).

It's a fairly large lens, as you might expect of an F1.7 constant-aperture zoom, but it's not overly heavy, so it handles well on cameras that have a decently sized hand grip.